At one point in the movie, Steppenwolf says he's going to conquer Earth "for Darkseid." And… that's it. Which isn't a whole lot, considering everything in this movie, not to mention the future dream sequences in Batman v Superman, sets up a future showdown with Darkseid, who is basically the DC Universe's version of Thanos.
For those who haven't read the comics, Darkseid is the ruler of the planet Apokolips. When it's mentioned that the Mother Box remakes the world in the image of Steppenwolf's home planet? That planet is Apokolips, where the Mother Box is from. And the Boom Tube, which is that teleportation tornado that whisks Steppenwolf around? Well, Apokolips is usually on the other end of that thing, which is probably where all those parademons keep coming from, though Steppenwolf was a little vague about exactly where he'd been for the last few thousand years.
In other words, Darkseid actually plays a major role in Justice League, he's just not seen or heard from, and is barely mentioned. Why? And what role will he have going forward? At this rate, it might be a long time before we find out.